Purification of anthracene



Patented Sept. l, 1936 l 'in Ulll'lgli-171)v "STATES PATENT oFFlcEVPURIFICATION OF ANTHRACENE Arthur H. Radasch, Bloomfield, N. J.,assgnor to The Barrett'Company, New York, N. Y., a corporation of NewJersey ,Application October 28, 1932, Serial No. 639,969

1 Claim.

terials free from dissolved impurities and in aV able pressure sinceitis generally 'more feasible" to operate at atmospheric temperaturewith corn-v paratively high pressure than atv atmosphericor slightlyhigher pressure and atv temperatures'com" side'rably below atmospheric.Furthermore, there is generally an increased solvent action ofthe liquidat normal atmospheric temperatures over that of the liquid whenmaintained at very low temperatures and under comparatively low pres'- 3sures.

IV have vdiscovered that such processes `and ap-` paratus 'usedj incarrying them out can beimproved and aV substantial saving effected inthe amount of heat required'for distillation` of the liquefied solventby compressing the puried'gas obtained in distillingY the impure liquidand us'- ing' its h'eat of condensation for distillation of furtheramountsfof solvent from the impure liq-` uid," whereupon the hotcompressed gases are cooled an'd'con'densed in Whole or'in' part toliquid form.

Among the objectsof myinvention are to provide an improved 'method' ofvpurifying materials,

to reduce the-cost of purifying and' recovering the solventu'sed inthe-process, to utilize heat pro'- du'ced-in, condensing' hot compressedgas in effectingui'stiuatio of impur-e liquefied` gas, and to reduce thecost-'ofconstucting and maintaining distillatin'apparatus for thepurification of the liquefied gas.' These and'other objects and featuresof'the invention Will appear from the following.fdescri-r'ntion`thereof` in 'which' reference is l madetothedrawing'illus'tratin'gV a'preferrdform :A of 'apparatus for carrying outthe process,

(Cl. 260-168l My invention relatesto a process and appara-4 Although myinvention is hereafter described as applied to the purification of crudeanthracene using liquid anhydrous ammonia as a solvent, it will beapparent that my invention is capable of wide application in treatinghighly vol- 5 atile solvents including liquefied gases otherfthananhydrous ammonia, or sulfur'dioxide, and may be used forpurifyingnumerous -materials other than anthracene.

In accordance'with my invention when used in 41()v purifyingcrude-anthracene by the selective solvent action of liquid anhydrousammonia, the anthracene is introduced into an extractor capablej ofwithstanding'high pressure. The extractor'is sealed and'the apparatusevacuated to re- 15 move air therefrom. Ammonia under sulicient pressuretojmaintain the same liquid under the conditions of operation .is then'introduced into the extractor and into contact with the anthracene. Thepressure ofthe ammonia" in the 20 extractorvvhen operating at normalatmospheric temperatures is ordinarily l about' 100 to 200 pounds persquare` inch, although this pressure may be varied-considerably asylongAas the ammonia Aused as a solvent is maintained in liquid 25 formr Y w Y.The ammonia and anthracene remain in contact until' the impurities,such as phenanthrene, carbazol, and other solid and liquid hydrocarbons,have been dissolved to thedesired extent, and the` 30 liquid ammoniacontaining' dissolved impurities is then- Withdrawn from the extractor.Preferably, the introduction of liquid ammonia into the extractor andthe removal of ammonia containing dissolved impurities therefrom iscarried out con- 3'5 tinuously, maintaining aph'arge of -liquid ammoniainf contact with the anthracene during op-V eration. The foregoingfstepsof the processmay be the same as the corresponding steps of. theprocess'fdescibed in^ the' copendingapplication 40 of StuartP. Miller,SeriaitNo'. 639968, nowPatent No.12,011,728,1 Aug.'20`,1935,9if desired.

*The liquid ammonia I containingY dissolved' impurities removed from'theanthracene is passed through an expansion valve to a distilling ap- 45paratus. The expansion valve employed is adaptedto maintain thenecessary high pressure in the extractorv while permitting thedistillation apparatus to be operated under'substantially lowerpressure; i. e'., a pressure substantially lower than pounds per squareinch or even at at- V'iosphericpressurespr'under vacuum, andl at acorrespondingly low temperature. 4

ammonia is distilled whereby substantially pure ammonia gas is producedand the impurities remain behind in the still. The ammonia gas thusproduced is removed from the distillation apparatus and compressed,preferably to a pressure about equal to that applied to the liquidammonia reservoir and extractor, say 100 to 200 pounds per squareinch.In compressingA the gas, the temperature thereof is raised and the heatof icondensation available at the higher temperature is utilized indistilling the impure liquid ammonia, l

preferably by passing the compressed and heated gas in heat exchangingrelation with the liquid ammonia yin the distillation apparatus.v Thisheat exchange causes the gas to be partially or Q Wholly condensed andmay also reduce its ternperature. The gas maybe further cooled incondensing apparatus to complete the liquefaction thereof and thecondensate is returned to thel liquid ammonia reservoir forrecirculation and reuse in the purification of the anthracene.

By the foregoing process I eliminate or reduce to a small amount thenecessity of using steam or external heat for distilling. the impureliquid ammonia, ,although if desired additional-heat may be supplied tothe distillation apparatus to supplement the heat available aftercompressing the ammonia gas.y V This feature of my invention is of I Y-compression, and condensation utilized to aid in the evaporation ofsolventfrom the extract.

Among solvents which can be handled in this manner may be mentionedsulfur dioxide (SO2) methyl and ethyl ethers v(CH3OCH3Y For example,crude anthracene may be purified according to my process byextractionwith acetone, instead of Ywith ammonia as described below, highertemperatures or lower pressures or' both being employed. as required bythe higher boiling point of acetone.

` The process hereindescribed'is preferably car-k ried out in apparatussuch as that shown in the figure of the drawing and hereinafterdescribed.

VThe apparatus shown in the drawing comprises a reservoir 2 in which ismaintained a supply of solvent consisting of a substance which isnormally gaseous or has a boiling point not greatly in excess ofatmospheric temperatures, and which, under pressure,is.in liquidv form.The solvent is delivered to anextractcr'd by means of a pump 6 throughpipe. 8.` The material to be purified, which iswsolid under-thewconditions of temperatureandpressure maintained in the extractor,is supported on a screen I0 in the lower portion of the extractor.Afterrsu'lcient Contact of the solvent and the solidto bepurified,

the solution of solvent and Iimpurities passes from the extractor 4 tothel distillation apparatus I2 through thedischarge pipeY I4 in which islocated an expansion valve I6 Yadapted to maintain the pressure in theextractor suiciently high to prevent distillation `or, gasification ofthe liquid Y solvent therein;k The expansion valve I6 also preand' lC2H5OC2H5) acetone (CH3COCH'3), and the like.

vents the pressure in the extractor from being.

communicated to the distillation apparatus so that the pressure underwhich distillation of the liquid ammonia containing dissolved impuritiesis carried out is relatively low and may not exceed atmosphericpressure. Y f

Ammonia gas filling tank I2 above the impure liquid ammoniais withdrawnfrom the distillation apparatus by a' compressor I8 through pipe 23 andis compressed to the desired pressure, say v100 to 200 pounds per squareinch. The compression of the gas causes the same to be heated and thehot compressed gas is passed through pipe 22, to a coil or other heatexchange device 24 located in the distillation apparatus in heatexchanging relation with the impure liquid am- Y monia to distill offammonia from the impurities dissolved therein. The compressed ammoniagas is thus cooled, may be partially or wholly condensed by heatexchange with the impure liquid ammonia and is passed through cooling'coilV 26 to insure complete'condensation of the ammonia to liquid form.The puried liquid ammoniais then returned to the reservoir 2Y forrecirculation and re-use in the cycle.

In the'starting operation of the apparatus, the material to be treatedis charged into the extractor and the extractor sealed. The apparatus isthen' evacuated to remove air *from the system and for this purpose thecompressorV I8V maybe employed for removing air'from the extractorthrough pipe 28 controlledby valve3, and from the distillation apparatusthrough pipe 20. air `Withdrawn, is discharged to theV atmospherethrough anexhaust vent 32. VWhen the appa'- ratus is evacuated, valve 30and the vent 32 are closed and valve 34 in the line 2,2`leading to heatexchange device 2,4 and the valve in pipe 20 are opened. Y The pump V6is Vthen operated to supply the liquid solvent to the extractor v4.Preferably the supply of solvent to the extractor and the discharge ofimpure liquid containing dissolved impurities from the extractor issubstantiallyfcon-V paratus after the solvent has been distilled oi aredrawn off through a drain 3G. The gas produced by distillation iswithdrawn by compressor I8 and compressed, and the resultant heated gaspassed therefrom to the coil 24 where the compressed gas gives upheat tothe impure solvent, distilling the same andr being thereby cooled andcondensed.V The condensate and any remaining un'condensed gas pass fromvheat exchanger 24 through the cooling coil 26, theresultant-puriedliquid extracting medium being returned tothe reservoir2.`

An auxiliary steam coil 31 may be provided in the distilling apparatusto make up heat losses from the system and aid inthe distillation of theammonia or other extracting medium when the heat of Vcondensation oftheammonia gas or other extracting medium in the coil 24 is insui'licientto vaporize the ammonia from thev impurities in still I2. For example,at the end of the distillation cycle, it may be that the heat ofcondensation of the ammonia gas in the coil V2li is insuiicient tovaporize the ammonia and thev impurities in still I2, and to supply thenecessary heat, steam coil 3l maybe utilized'. It will be understood,however, that' the major portion of the heat required to distill therammonia from'the impurities comes Thev ioY

from the heat of condensation of the ammonia by indirect heat exchangebetween the hot compressed ammonia gas in coil 24 and the liquid instill I2. The steam coil 31 may also be employed in the heating up andmelting of the impurities in the still and assisting in their removalfrom the still.

My invention is adapted for use in the treatment of liqueed gases otherthan those used as solvents, and the process may be carried out inapparatus other than that herein shown and described. It should,therefore, be understood that the foregoing description is intended tobe illustrative and is not intended to limit the in vention.

The term liquefied gas as used in this specication is intended toinclude highly volatile solvents in liquid form, examples of which aregiven above.

I claim:

'I'he method of purifying crude anthra-cene which comprises introducinganthracene to be treated into an extractor, evacuating said extractor,sealing the extractor and continuously introducing liquid anhydrousammonia under a pressure of about 100 to 200 pounds per square inch intothe extractor into contact with the anthracene to dissolve impuritiesfrom the anthracene, continuously removing liquid ammonia containingdissolved impurities from the extractor and passing the same todistillation apparatus maintained at a pressure substantially less than100 pounds per square inch, distilling the impure liquid ammonia toseparate substantially pure ammonia gas from the impurities dissolved inthe liquid ammonia, compressing the ammonia gas thus produced wherebythe gas is heated, passing the com-- pressed and heated gas through azone immersed in the impure liquid ammonia in the distillation apparatusto distill the liquid ammonia and cool the gas, condensing andcollecting purified liquid ammonia thus produced and passing the liquidammonia again into contact with the anthracene.

ARTHUR H. RADASCH.

